You can redirect stdin, but that doesn't disassociate the process from the controlling terminal: $ tty /dev/pts/1 $ tty < /dev/null not a tty $ ps

You can redirect stdin, but that doesn't disassociate the process from the controlling terminal: $ tty /dev/pts/1 $ tty < /dev/null not a tty $ ps -q $$ -o tty= < /dev/null pts/1 The other file descriptors referring to the terminal don't matter either: $ sh -c 'pid=$$; tty=$(ps -q $pid -o tty=); echo "$tty" > /dev/tty' <&- >&- 2>&- pts/1